[llvm] [VPlan] Run initial recipe simplification on VPlan0. (PR #176828)

[Ramkumar Ramachandra via llvm-commits]

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@@ -8122,6 +8122,8 @@ void LoopVectorizationPlanner::buildVPlansWithVPRecipes(ElementCount MinVF,
       Legal->getReductionVars(), Legal->getFixedOrderRecurrences(),
       CM.getInLoopReductions(), Hints.allowReordering());
 
+  VPlanTransforms::simplifyRecipes(*VPlan0);
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artagnon wrote:

What happens if you move this near the beginning of tryToBuildVPlanWithVPRecipes, before creating wide recipes with predication? I think we'd get the same optz results, and it would save us from special-casing no-vector-loop-region in simplifyRecipe?

https://github.com/llvm/llvm-project/pull/176828